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September 22, 2021     Post 130
More Bar Talk-Fossil stories



Beach Pebble Fossils and Climate Change

I will have ordivician era fossil pebbles to share at my Sept 30 book signing Rivers End Books Oswego 5 to 7pm for “A Natural History of Lake Ontario”

Do we live in a time of reliable God given order?’ Or can our globe’s climate abruptly and profoundly change in a matter of years or even months? A visit to the neighborhood (barrier) bar provides a few clues.

The great Ordovician extinction stands out among major mass extinctions in being unambiguously linked to climate change. During this event about 440 million years ago 85% of earth’s living species of animals were wiped out. It had a far more severe ecological impact than the K-T event that finished off the dinosaurs.

During the Ordovician Era Lake Ontario’s watershed was covered by a warm sunlit shallow sea. At this time all of earth’s larger more complex creatures were marine. Life in the form of crinoids (sea lilies), corals, graptolites, snail like gastropods, clam like brachiopods, and a variety of cephalopods with shells that were ancestors to todays cuttlefish and nautoloids, along with other creatures swarmed in the shallows. Evidence from the fossil record shows that an abrupt change in climate caused the second most severe mass extinction of this thriving community of life in earth’s history.


Complex systems seek equilibrium. Ecologists refer to the condition of homeostasis to describe the tendency of nature to ‘self correct’ when pushed out of balance. However, when complex systems like a lake or a terrestrial ecosystem are pushed too far out of one equilibrium state, they can flip suddenly into another. And often these complex systems push past a tipping point into a new condition more readily than they can return to the prior state. Frequently after a transition has happened, it remains in it’s new state for a long period before establishing anything like the previous condition.

About 440 million years ago, for some as yet unknown reason, the amount of CO2 in the atmosphere decreased. Earth’s climate cooled and a global ice age followed. Cooling temperatures and falling sea levels caused by water being locked up as ice in vast glaciers then wiped out the vast majority of marine life then in existence. As we entered the Silurian age, marine life slowly began to recover. But most of the fossils we see today in Lake Ontario beach pebbles are of extinct life forms.


It took about five million years for the ancient seas to recover their biodiversity of animals. (The fossil pebble in this photo shows a 'hash' of fragmented marine animals, probably at leasst two or three types.)

No one knows exactly what triggered this long ago ice age. One theory holds that the invasion of dry land by plant life reduced the CO2 in the atmosphere. Another theory holds that intense volcanic activity might have produced immense flows of chemically active rock that reacted with the carbon dioxide in the air to form carbon rich minerals like calcite. Paleontologists believe either of these scenarios could have kicked off an ice age. No one knows how quickly it happened either, but there is some suggestion that the tipping point into arctic conditions might have happened on a human lifespan time scale.


When the ‘green house effect’ of global warming from fossil fuel use first became an area of active scientific research, most people thought of it as a gradual linear warming that took place over thousands of years. But technology and more powerful analytic tools and computers allowed the collection of new data in the 1970s that began to suggest the change might not require thousands or hundreds of years. More recently studies of ancient ice cores showed that global climate could indeed shift radically within a century. Considerable evidence exists that the shift possibly took place over just a decade or two. And there seem to be feedbacks that could make warming self-sustaining.

Today data suggests that possible "tipping points" for an irreversible, rapid and catastrophic climate change exist if greenhouse gas emissions continued to rise.

The good news from the great extinction of the Ordovician seas where now Lake Ontario’s waves roll, is that the animal life of ancient times did recover. But it took 5 million years. That’s roughly forty times longer than the entire 200,000 year history of our own human species. So some prevention through individual and collective social action might be the best cure. And it’s high time we got serious about it.
More coming soon on beach pebble fossils...



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